Magnetic seal for floating roof



April 25, 1961 A. F. FlNO ETAL MAGNETIC SEAL FOR FLOATING ROOF 2 Sheets-Sheet 1 Filed Feb. 4, 1960 FIG.2

FIG.3

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Filed Feb. 4, 1960 INVENTORJ Alexander F. Fino John M.Swick ATTORNEY 2,981,436 MAGNETIC SEAL FOR FLOATING ROOF Filed Feb. 4, 1960, Ser. No. 6,764 12 Claims. '(Cl. 220-26) This invention relates in general to floating covers or roofs for tanks and pertains, more particularly, to novel sealingmeans therefor.

It has been a problem in the art for many years to assure an effective and adequate seal between floating roofs and the tanks within which they are confined and which they protectively cover. This is due to many factors, including such variables as uniformity of the tank wall structure and weather conditions such as, for example, the presence or absence of ice and snow. It is, in general, conventional to employ a roof structure which is of smaller diameter than the inside ,diameter of the tank and to provide extending radially therefrom some generally flexible means which engages the inside of the tank wall to form the proper seal. However, such flexible sealing means are usually of a fairly complex nature and are generally formed entirely separtely from a secondary sealing means normally referred to as a weather shield which tends to deflect water and other precipitation or foreign material centrally towards the physical confines of the roof itself and away from the space between the roof and the tank. Although weather shields may be of relatively simple construction and design such as will permit their easy removal and inspection, the primary seals which are usually located adjacent the lower edge of the roof are normally of such complexity, size and ch'ar-' acter as to preclude a ready inspection and removal thereof while the tank is in service.

It is, therefore, of primaryconcern in conjunction with the present invention to provide an improved form of seal for the floating roofs of tanks which will be entirely adequate and effective in service and which, at the same time, is capable of inspection and removal while the tank is in service, these results being achieved by virtue of the use of magnetic means for achieving the sealing effect.

Another object of this invention is to provide an improved seal for the floating roofs of tanks in which the seal assembly is an integrated assembly, including not only a weather shield, but also a primary seal capable of accommodating for varitions in the diameter of the tank at various elevations therein and in which there is a peculiar and specific cooperation, heretofore unknown, between the primary seal and the weather shield rendering both seals as a unit more effective and adequate.

A further object of this invention is to provide a novel arrangement of component parts for effecting a'seal between a floating roof and its associated tank and in which certain flexible elements are so physically associated with each other and with magnetic means as well as a relatively stiff weather shield as to admirably perform a sealing action under any and all conditions and in conjunction therewith, there being novel anchoring means tending to prevent damage to the seal during downward movement of the roof should frozen moisture accumulate between the seal and the tank tending to adhere thetwo together.

Further, it is an object of this invention to provide a novel seal assembly in which the same maybe easily inspected and replaced during the time when the tank is which are located in the rim space area and which, as a" result, take up a certain amount of physical space therein. This type of connecting means includes some sort of resilient or spring means for urging the conventional seals into engagement with the tank wall, therefore, considerably restricting the amount of physical movement of which the seal is capable. Consequently, under aggravated conditions such as unusual descrepancies in the contour of the tank wall, present seals cannot properly and effectively achieve their desired end result since their movement and conforming adjustment do not have a sufficient degree of freedom to enable them to effect the proper seal under aggravated conditions. According to the present invention, however, all connecting apparatus, clips, springs and the'like which are usually located in the rim space area are eliminated, thus enabling the full Working space for adjustment of the seal so that at all times it may achieve a proper and effective sealing action.

Additionally, the seal in accordance with the present invention is not restricted in physical limits to expansion or contraction and accommodates for variations in distances between the roof and the wall of the tank within those limits which would normally be encountered in service regardless of the degree of variation within such practical limits. The magnetic elements will follow the tank wall for all required variations, whereas with conventional seals, the conformity thereof with the surface of the tank wall is limited by the action of the mechanical device exerting an outward or spring force on the seal or by the internal supporting structure of the sealing mechanism.

The invention arrangement is also highly advantageous due to the novel construction thereof which permits the roof itself to rise above the upper edge of the tank while maintaining an effective seal therewith thereby enabling the utilization of the full storage volume of the tank. This is accomplished by providing a novel means of suspending the sealing means from the roof whereby the portion of the seal which engages the tank wall when the roof is above the top edge of the tank is effectively supported by a portion of the weather shield of the' sealing means.

In the drawings:

Fig. 1 is an elevation partly broken away of a storage tank with a floating roof therein, the novel sealing means of the present invention being operatively associated with the roof of the tank;

Fig. 2 is an enlarged perspective broken away view of a portion of the roof and tank illustrating the manner in which the sealing means is mounted in operative position;

Fig. 3 is another enlarged perspective partially broken away view illustrating the roof extending above the upper edge of the tank;

Fig. 4 is a sectional view illustrating a portion of the tank and roof with the sealing means in operative position;

Fig. 5 is an enlarged view of a portion of Fig. 4, illustrating the manner of supporting the inner portion of the weather shield;

Fig. 6 is a sectional view illustrating the roof in position extending above the upper edge of the tank;

Fig. 7 is a sectional view showing the position of the sealing means during downward movement of the roof wherein the portion of the sealing means contacting the tankmay be frozen or adhered thereto; and

' Fig. 8 is an enlarged view of the lower portion of the Patented Apr. 25, 1961-,

sealing means illustrating a modification of the invention.

Referring now to the drawings, Fig. 1 illustrates a conventional tank indicated generally by reference numeral 10 which is adapted to store gasoline, oil and the like, the tank being of conventional construction and including an outwardly extending flange 10' at the upper end thereof defining the upper edge portion of the tank. A floating cover or roof is indicated generally by reference numeral 11, the roof being of substantially circular configuration and having a diameter less than that of the tank, the sealing means of the present invention being adapted to seal the annular space between the roof and the tank. The roof or cover floats on the upper surface of the tank in a well-known manner, and accordingly rises and falls with the level of the liquid within the tank.

a The roof 11 is of relatively simple Construction and includes a cylindrical outer wall 12, a lower circular wall 13 being sealingly secured to the lower edge of wall 12, and an upper circular wall 14 being secured to the inner surface of wall 12 at a point spaced below the upper edge thereof. It will be noted that the upper edge of cylindrical wall 12 includes an inturned annular flange 16.

As mentioned previously, the sealing means of the present invention includes a weather shield which slopes upwardly. and outwardly of the. roof in such a manner as to cause rain water and such to drain toward the center of the roof whereat it is removed from the roof by conventional means (not shown). The sloping weather shield of the present invention is of annular configuration and includes an inner marginal edge 17 and an angularly related intermediate. portion 18 which is of relatively stiff construction such that it will remain in the proper operative position as shown in the drawings during operation. An outer marginal edge. portion 19 extends integrally from the outer edge of intermediate portion 18, the outer edge portion being considerably more flexible than the intermediate portion 18, and being so constructed and arranged that it inherently tends to flex outwardly due to its natural resilience.

The weather shield is preferably constructed of rubber or similar material and the outer marginal edge portion.

19 is preferably provided with more rubber than the intermediate portion 18 to provide the characteristics mentioned above. This natural resilience of portion 19 normally tends to carry the outer edge of the weather shield toward the inner surface of the tank so as to produce a seal with the tank. An annularly extending curtain means provides the primary seal between the roof and the tank,the curtain means including an inner portion 20 having the top edge thereof seated upon theupper edge of flange 16. The curtain means also includesan'outer portion 22 disposed adjacent. the inner. wall of the. tank and an intermediate portion 24'extending between the lower parts. of portions 2,0. and 22. As shown, portions 20, 22 and 24 are separate members which are suitablysecured to one another, it beingi'evident that the various portions may be formed integral as one sheet, if desired. As seen most clearly in Figs. 2, 3 and 5, for example,

an annular support strap or restraining flange 2 8 is provided, member. 28 including 'aninner flangeportion 29 and an angularly disposedouter flange portion 31.' The inner flange portion 29 of the restraining flange is disposed in overlying relationship to the upper edge 21 of the inner portion. of the curtain, and the innermost flange portion 17 of the weather shield is disposed in overlying relationship to inner flange portion 29'. The entire assembly including the portions 17, '29, 2 1 andf16; are maintained in operative position by rneans ofthreaded studs 36 which are secured to inturne d flange 16, the

studs, extending; up through. suitable. openings in the various members and throughopenings in an annular clamping plate 17 disposed in oyerlyingrelationship to the intier portion 17 of' the, weather shield. [Suitable nuts37 te-meanest, n. thef nne' g e i1 hrsadd tu 0 assume 4 maintaining the entire assembly in tight sealed relationship.

An upper annular edge portion 22' of the outer portion 22 of the curtain is secured to the flexible outer portion 19 of the weather shield by cementing or the like to support the outer edge of the curtain from the upper edge portion of the weather shield. Preferably, the curtain means including portions 20, 22, and 24 are formed of synthetic sheet orflexible plastic or like material.

The means for retaining the inner portion and outer portion of the curtain means in sealing contact with the tank and roof comprises magnetic means 23 and 30 respectively. The cylindrical wall 12 of the roof as well as the wall of the tank are formed of steel or similar metallic material whereby the magnetic means 23 and 30 are continually attracted thereto.

Each of magnetic means 23 and 30 defines an annular strip of magnetic material which has a substantial width and is of relatively small thickness as 'seen' in the drawings, each of the means extending in an annular strip within the curtain means. Each of the annular means may comprise a plurality of strips placed in end-to-end relationship with one another, the inherent magnetic characteristics of the strips retaining them in proper operative position. The magnetic means 23 and 30 may be formed of a suitable magnetic rubber-like material which, for example, may comprise a product named Denmag, made by the Deriman Rubber Company, P.O. Box 951, Warren, Ohio. The magnetic means may also be formed of annular bands of flexible magnetic material as disclosed in Patent No. 2,627,097 to R. Ellis, issued February 3, 1953, wherein the flexible strips are formed of rubber or similar flexible material having magnetizable particles inherently mixed therein.

In assembling the apparatus, the inner edge of the inner curtain portion 20 is first clamped in operative position by means of plate 17' whereupon annular means 30 and,

vided with a width, when'in the operative position as shown, which is substantially greater than the normal spacing between the outer portion of the roof and the inner surface of the tank. This permits the dimension of the annular space to vary within wide limits thereby compensating foreccentricity of the roof with respect to the tankwithout pulling away the magnetic portions 30 or 23 from a point adjacent the associated walls of the roof and the tank.

Secured to the curtain adjacent the bottom part of inner portion 20 of the curtain are a plurality of circumferentially spaced straps 25, each of which is provided with a looped free end portion which is engaged over hooks 26 fixed to the under surface ofthe roof as shown, the straps serving a purpose hereinafter described.

Referring now to Fig. 8 of the drawing, a modification is illustrated wherein like portions have been indicated by the same reference numerals primed. The sealing means between the roof wall 12" and the tank wall 10' includes a curtain formed of an innerportion 20', an intermediate portion 24' and an outer portion 22' which are supported in the same manner discussed in connection with the aforedescribed modification,

Sealing means 3Q and 23 are similar to sealing means 30 and 23 respectively as described hereinbefore, the pri-, mary distinction of this modification over the previously described modification being the provision of an annular strip ofmtaterial 4 0 which may have a substantially recans' r weeten n amber! nd ncludin sp e ite faces 41 and 42 which are disposed in abutting-relation ship with the adjacent surfaces of magnetic means 30' and 23' respectively. Body means 40 may be formed of a suitable material such as polyethylene foam and is adapted to serve as a spacer for maintaining the sealing means in the spaced position as shown so that the sealing means will be maintained in the operative position shown in Fig. 8 during normal operation of the apparatus.

Referring again to Fig. l, the roof is disclosed in its normal operative position wherein the roof is disposed below the upper edge 10' of the tank. In this position, the resiliency of portion 19 of the weather shield urges this outer edge of the weather shield as Well as the cemented portion of the outer part of the curtain against the inner surface of the tank to effect a good seal therewith. It is evident that the resilient outward force of portion 19 tends to take up variations in the space between the roof and the inner wall of the tank. As mentioned previously, it is a particular object of the invention to provide an arrangement which permits maximum utilization of the storage space within the tank itself. This is accomplished in the present invention due to the fact that magnetic means 23 will retain the outer portion 22 of the curtain in sealing engagement with the wall of the tank even when the roof has moved a substantial distance above the upper edge of the tank as illustrated for example in Figs. 3 and 6. This mode of operation is possible due to the novel manner of suspending the outer portion of the curtain from the outer edge of the weather shield. The weather shield although being of relatively flexible construction is enabled to support the curtain seal in operative position due to the fact that the intermediate portion 18 thereof is of relatively stiff construction, the stiifness of the intermediate portion 18 being enhanced by the provision of reinforcing ribs R as seen most clearly in Fig. 2 which extend outwardly of the roof along the major part of intermediate portion 18 of the weather shield, the ribs R being located at spaced circumferential points along the weather shield. Ribs R may comprise a suitable rigid means such as metallic strips or bars which are suitably secured to the material of intermediate portion 18 of the weather shield. In addition, the outer flange portion 31 of restraining flange 28 further supports the inner part of intermediate portion 18 to ensure that it remains in the upright position illustrated in Figs. 3 and 6 when the roof rises above the upper edge of the tank. It will be observed that when the tank is in such elevated position, the outermost portion 19 of the weather shield bows outwardly due to its natural resilience.

. As seen most clearly in Figs. 2 and 4, when the sealing means is in normal operation, thelower part of the outer curtain portion 22' will be urged into'sealing engagement With the wall of the tank by magnetic means 23, and the initialstages in Fig. 7, will very advantageously separate upper part of the outer portion 22 will normally hang in the position shown such that it is spaced a small distance from the inner wall of the tank, this space being indicated by letter S.

During downward movement of the roof as, .for example, is shown in Fig. 7, there will be a tendency for the roof to move first without imparting a corresponding movement of the outer curtain portion 22 and this can occur to varying degrees depending upon conditions until such a situation as is specifically shown in Fig. 7 occurs. In Fig. 7, the roof has moved downwardly a sufficient extent to impart substantially a taut condition to the bottom portion 24 of the curtain which tends to pick the lower extremity of the outer curtain portion 22 away from the surface of the tank as indicated by the reference character 35. At the same time, as soon as the bottom portion 24 isfully tensioned, a further and further peeling action of the curtain 22 will occur until the entire curtain may become tensioned. This is particularly advantageous should the. outer curtain become frozen to the tank as can sometimes occur in cold weather. In this case, the sealing action shown in its the outer curtain from the tank without imparting undue strain thereto such as might otherwise occur were not the peeling action present.

On the other hand, during downward movement of the deck or roof, it will be appreciated that the relatively stifi weather shield 18 will move downwardly relatively quickly and substantially instantaneously as the deck or roof moves down. Should, however, the weather shield be frozen to the tank, the weight of the roof will positively peel the Weather shield away from the tank wall and a continued peeling action will also occur as the roof drops further.

This continued peeling action by the weather shield will pull that part of the curtain portion 22 which is above magnetic means 23 away from the wall of the tank. The magnetic means 23 has sufficient weight so that it always tends to slide down along the tank shell and accordingly, the adjacent area of the outer curtain portion 22 will tend to pull away from the tank wall.

It will be evident that when it is desired to inspectthe seal structure, a person can reach down through the space between the roof and the tank to remove the straps 25 from the hooks 26. The entire curtain structure may then be pulled up out of the annular space be- ,tween the roof and the tank for inspection and for redirection of movement of the roof, and regardless of.

the relative positions of the members, an effective seal is maintained between the roof and tank at all times.

The construction permits the roof to rise a substantial distance above the upper edge of the tank thereby providing a maximum utilization of the storage space within the tank and at the same time an effective seal is maintained with the tank.

' The apparatus of the present invention is relatively simple and economical in construction, and yet is eflEec-- tive and reliable in operation. As this invention may be embodied in several forms without departing from the spirit or essential characten. istics thereof, the present embodiment is therefore illustrative and not restrictive, and since the scope of the invention is defined by the appended claims, all changes that fall within the motes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents are therefore those claims.

We claim: l. A seal for a floating roof tank in which a generally intended to be embraced by cylindrical tank is provided with a cylindrical floatingv roof therewithin of a diameter less than the inside diameter of the tank, the seal comprising an annular relatively stiff weather shield flexibly connected at its-inner marginal edgeto the roof structure and having a flexible.

marginal outer edge for sealing engagement against. the inner surface of the tank, an outer curtain of flexible material in the form of an annular band secured along its. upper marginal edge adjacent the outer marginal edge of said weather shield and hanging therefrom in close proximity to the inner surface of the tank, magnetic means carried by said outer curtain along the lower marginal edge thereof attracting the curtain toward the inner surface of, said tank, an inner curtain in the form of an annular'band of flexible material secured along its upper marginal'edge to the roof structure and hanging therefrom from a point adjacent the point of attachment between the inner mar ginal edge of the weather shield and the roof, magnetic means carried by the lower marginal edge portion of said inner curtain attracting the same towardsaid roof structure, and a flexible bottom sheet'in the form of a generally horizontal annulus having its inner and outer edges secured respectively to the inner and outer curtains.

2. A seal for a floating roof tank in which a generally cylindrical tank is provided with a cylindrical floating roof therewithin of a diameter less than the inside diameter of the tank, the seal comprising an annular relatively stiff weather shield flexibly connected at its inner marginal edge to the roof structure and having a flexible marginal outer edge for sealing engagement against the inner surface of the tank, an outer curtain of flexible material in the form of an annular band secured along its upper marginal edge adjacent the outer marginal edge of said weather shield and hanging therefrom in close proximity to the inner surface of the tank, magnetic means carried by said outer curtain along the lower marginal edge thereof attracting the curtain toward the inner surface of said tank, an inner curtain in the form of an annular band of flexible material secured along its upper marginal edge to the roof structure and hanging therefrom from a point adjacent the point of attachment between the inner marginal edge of the weather shield and the roof, magnetic means carried by the lower marginal edge portion of said inner curtain attracting the same toward said roof structure, a flexible bottom sheet in the form of a generally horizontal annulus having its inner and outer edges secured respectively to the inner and outer curtains, said bottom sheet being of a width substantially greater than the spacing between said roof and said tank.

3. A seal for a floating roof tank in which a generally cylindrical tank is provided with a cylindrical floating roof therewithin of a diameter less than the inside diameter of the tank, the seal comprising an annular relatively stifi weather shield flexibly connected at its inner marginal edge to the roof structure and having a flexible marginal outer edge for sealing engagement against the inner surface of the tank, an outer curtain of flexible material in the form of an annular band secured along its upper marginal edge adjacent the outer marginal edge of said weather shield and hanging therefrom in close proximity to the inner surface of the tank, magnetic means carried by said outer curtain along the lower marginal edge thereof attracting the curtain toward the inner surface of said tank, an inner curtain in the form of an annular band of flexible material secured along its upper marginal edge to the roof structure and hanging therefrom from a point adjacent the point of attachment between the inner-marginal edge 'of the weather shield and the roof, magnetic means carried by the lower marginal edge portion of said inner curtain attracting the same toward said roof; structure, a flexible bottom sheet in the form of a generally horizontal annulus having its inner and outer edges secured respectively to the inner and outer curtains, strap means secured to and hanging from the lowermarginal edge of said inner curtain, there being hooks-disposed on the undersurface of said roof with which said straps are engaged.

4. In a liquid storage tank having a cylindrical outer wall and a cylindrical floating roof therewithin with there being an annular space between the roof and the inner surface of said wall, a seal assembly carried by said roof 8 5. In a liquid storage tank having a cylindrical outer wall and acylindrical floating roof therewithin with there and engageable with the inner surface of said outer wall,

said seal including a weather shield extending upwardly and outwardly from the periphery of said roof for contact along its outer edge with the inner surface of said outer wall, inner and outer flexible curtain members attached adjacent the inner and outer edges respectively of said weather shield and hanging therefrom respectively along the outer surface of said roof and the inner surface of said outer wall, a flexible bottom sheet interconnecting said curtains along the lower edges thereof, magnetic means attached to the lower edges of said curtains for holding the same i-n contact respectively with said roof and the inner surface of saidouter wall.

being an annular space between the roofand the inner surface of said wall, a seal assembly carried by said roof and engageable with the inner surface of said outer wall, said seal including a weather shield extending upwardly and outwardly from the periphery of said roof for contact along its outer edge with the inner surface of said outer wall, inner and outer flexible curtain members attached adjacent the inner and outer edges respectively of said weather shield and hanging therefrom respectively along the outer surface of said roof and the inner surface of said outer wall, a flexible bottom sheet interconnecting said curtains along the lower edges thereof, magnetic means attached .to the lower edges of said curtains for'holding the same in contact respectively with said roof and the inner surface ofsaid outer wall, said magnetic means being in the form of annular bands of rubber having magnetic particles embedded therein.

6. In a liquid storage tank having a cylindrical outer wall and a cylindrical floating roof therewithin with there being an annular space between the roof and the inner surface of said wall, a seal assembly carried by said roof and engageable with the inner surface of said outer Wall, said seal including a weather shield extending upwardly and outwardly from the periphery of said roof for contactalong its outer edge with the inner surface of said outer wall, inner and outer flexible curtain members attached adjacent the inner and outer edges respectively of said weather shield and hanging therefrom respectively along the outer surface of said roof and the inner surface of said outer wall, a flexible bottom sheet interconnecting said curtains along the lower edges thereof, magnetic means attached to the lower edges of said curtains for holding the same in contact respectively with said roof and the inner surface of said outer wall, a plurality of straps fixed to the lower edge of said inner curtain and depending therefrom, each strap terminating in a loop, and a plurality of hooks fixed to said roof and over which the loops of said straps are engaged.

7. In a liquid storage tank having a cylindrical outer wall and a cylindrical floating roof therewithin with there being an annular space between the roof and the inner surface of said wall, a seal assembly carried by said roof and engageable with the inner surface of said outer wall, said seal including a weather shield extending upwardly and outwardly from the periphery of said roof for contact along its outer edge with the inner surface of said outer wall, inner and outer flexible curtain members attached adjacent the inner and outer edges respectively of said weather shield and hanging therefrom respectively along the outer surface of said roof and the inner surface of said outer wall, a flexible bottom sheet interconnecting said curtains along the lower edges thereof, magnetic means attached to the lower edges of said curtains for holding the same in contact respectively with said roof and the inner surface of said outer wall, said weather shield having a flexible inner marginal edge portion fixed to said roof, a stiff intermediate portion and terminating at its outer marginal edge in a flexible portion for deformed engagement with the inner surface of said outer wall, a supporting straphaving a rigid annular inner portion fixed to said roof underlying said inner marginal edge portion of the weather shield and having a rigid upwardly and outwardly directed outer edge portion underlying a portion of said intermediatev portion of the weather shield to support the same when its outer marginal edge portion is out of contact with said outer wall.

8. In a liquid storage tank having a cylindrical outer wall and a cylindrical floating roof therewithin with there being an annular space between the roof and the inner surface of said wall, a seal assembly carried by said roof and engageable with the inner surface of said outer wall, said seal including a weather shield extending upwardly and outwardly from the periphery of said roof for contact along its outer edge with the inner surface of said outer wall, inner and outer flexible curtain members attached adjacent the inner and outer edges respectively of said weather shield and hanging therefrom respectively along the outer surface of said roof and the inner surface of said outer wall, a flexible bottom sheet interconnecting said curtain along the lower edges thereof, magnetic means attached to the lower edges of said curtains for holding the same in contact respectively with said roof and the inner surface of said outer wall, said weather shield having a flexible inner marginal edge portion fixed to said roof, a stilf intermediate portion and terminating at its outer marginal edge in a flexible portion for deformed engagement with the inner surface of said outer Wall, a supporting strap having a rigid annular inner portion fixed to said roof underlying said inner marginal edge portion of the weather shield and having a rigid upwardly and outwardly directed outer edge portion underlying a portion of said intermediate portion of the weather shield .to support the same when its outer marginal edge portion is out of contact with said outer wall, a plurality of straps fixed to the lower edge of said inner curtain and depending therefrom, each strap terminating in a loop, and a plurality of hooks fixed to said roof and over which the loops of said straps are engaged.

9. In combination, a substantially cylindrical tank, a substantially cylindrical floating roof disposed in said tank and having an outer diameter less than the inner diameter of said tank, and sealing means disposed between said roof and said tank, said sealing means comprising an annular Weather shield means secured to the upper portion of said roof and extending upwardly and outwardly with respect to said roof for engagement with the inner surface of said tank and being of a relatively stiff material, curtain means supported by said roof and including a first inner portion, the inner portion being supported at the upper outer edge portion of the roof and depending adjacent to the outer surface of the roof, said curtain means including an outer portion supported on the upper outer edge portion of said weather shield and depending adjacent the inner surface of said tank, said inner and outer portions being joined by an intermediate portion, and magnetic means associated with said inner portion and said outer portion for retaining said inner and outer portions in contact with the outer surface of said roof and the inner surface of said tank respectively.

10. Apparatus as defined in claim 9, wherein said magnetic means includes a first substantially annularly extending body of magnetic material having a substantial width and a relatively small thickness, said first body of magnetic material engaging the inner surface of said outer portion, said magnetic means also including a second substantially anularly extending body of magnetic material disposed in engagement with the surface of said inner portion which is opposite to the surface thereof in engagement with the outer surface of said roof.

11. Apparatus as defined in claim 10, including a substantially annularly extending body of material disposed between and abutting the lower portions of said bodies of magnetic material for maintaining the bodies of magnetic material in spaced relationship.

12. Apparatus as defined in claim 9, wherein the outer periphery of said weather shield is so constructed and arranged as to be much more flexible than the main body portion thereof whereby the outer periphery of the weather shield is resiliently urged in a direction radially outwardly of said roof to ensure an effective seal with the inner surface of said tank.

No references cited. 

